Antenna system



June 29, 19379 H. J. LOFTIS ET AL ANTENNA SYSTEM Filed June 15, 1932 2Sheets-Sheet l HUMEH J LUF T15 IZQL H/CE F/f CHHTh Y a n g? ANTENNASYSTEM ZSheets-Sheet 2 Filed June 15, 1932 Wm H a 5 a 5 1 M 4 z an 2 T mM Z 2 H W m mflmr fi a C 2 fibi\\-\ c. w N uh ni n. 5. it a? MP mm 2 a aI! 1.. 1 1 a H H W a u 1 m w 44 a m, m m;

Patented June 29, 193? ANTENNA. SYSTEM Homer J. lloftis, llronton, andMaurice F. Mc-

Carthy, Dayton, 0 signincnts, to

in, assignors, by mesne o Corpcraticn of America,

This invention relates to an antenna system, and more particularly to anantenna system which tends to eliminate noise and interference fromlocal disturbances, and to which more than one receiver may beconnected.

The problem of providing a good antenna for use in apartment houses orcongested districts as Well as the elimination of interference fromstreet cars, elevators, electrical machinery and motors has long been avexing one. A great many unsuccessful noise eliminating systems havebeen devised, and some elaborate and expensive means have been devisedto solve the apartment house antenna problem. And, more economical meanshave been proposed to solve the antenna problem for apartment houses andhotels, but they have not done anything toward the problem of noiseelimination.

A system which requires the use of booster amplifiers is expensive infirst cost, a tinual expense because vacuum tubes must be replaced andpower is consumed in the operation.

The systems which are economical in installation and operating cost, butwhich do not eliminate or even tend to eliminate stray noises areusually quite unsatisfactory in apartment houses and hotels because ofthe electrical apparatus usually present and utilized in and about thoseplaces.

It is an object of the present invention to provide an antenna systemwhich may have more than one outlet. This has been accomplished byproviding an antenna system having a trans" mission line and a couplingdevice connected to the transmission line for each desired outlet.

Another object of this invention is to provide an antenna system whichwill tend to eliminate stray signals, or interference which is pickedup. rhis has been accomplished by close association of the conductors ofthe transmission line and balancing and shielding the coupling devices.

Another object of this invention is to provide an antenna system whichmay have a large number of receivers connected thereto and which willpermit good signal reception by all of the receivers withoutnecessitating the use of a booster amplifier. This has been accomplishedby providing coupling devices to properly match the impedances of thesystem.

Another object of this invention is to provide an antenna. system whichis easy and economical to install in either a building which is beingbuilt, or one which is built and is in use.

Another object of this invention is to provide an antenna system whichrequires little or no attention or expense after installation.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of one form of the invention isclearly shown.

In the drawings:

Fig. 1 discloses the circuit for the coupling dcvices and connectionsfor an antenna system of the type to be described in the presentspecification.

Fig. 2 is a sectional View showing a preferred construction for one ofthe coupling devices used in this system.

Fig. 3 is an enlarged fragmentary sectional view taken substantially ona line 3-3 of Fig. 4.

Fig. 4 is a sectional view disclosing the construction details of apreferred form of another type of coupling device used in the system.

Fig. 5 is a combination circuit and structural drawing showing a methodof installing the system with different types of coupling devices forcoupling the transmission line to a radio device.

Fig. 6 is an enlarged fragmentary sectional View take substantially on aline "5-5 of Fig. 4.

With particular reference to Fig. 1, an inductance or winding ill isconnected in series with an antenna 1 and a counterpoise 2. Windings i iand i5 are preferably wound parallel, coaxial and adjacent. One end ofthe winding it is connected to an end of the winding it through a leadit so that the magnetic fields of the two windings aid. A winding 29formed by the windings M and iii thus connected in series, ismagnetically coupled to the winding iii. A shield 12 is interposedbetween the windings la and 2d, and connected to the winding it!intermediate that winding and the counterpoise 2. The assembly thusformed serves as a coupling or impedance matching device 22. A metallichousing 2 enclosing the coupling device 22, and connected to the Windingii) intermediate that winding and the counterpoise 2, forms a shield forthe device. A transmission line iii is formed by conductors 26 and 28,which conductors are preferably insulated and closely associated ortwisted. The transmission line 36 is connected to the extremities of thewinding 2!), and serves to carry signal energy.

The reference numerals 3 and 3% refer to coupling devices which aresimilar in structure, and like numerals will refer to similar parts ofthose devices. The extremities of a balanced winding 38 are connected tothe conductors 253 and 23 of the transmission line 353 through leads l2and M respectively. The balanced winding 33 is preferably formed by twowindings M and d6 wound parallel, coaxial and adjacent, and connected inseries through a lead 48 so that their magnetic fields aid. A winding5%] is magnetically coupled with the winding and adapted for connectionto a radio device through leads 52 and 54!, connected to the extremitiesof the winding. A shield is interposed between the windings 38 and 5band connected to an extremity of winding 59 intermediate that windingand the lead 54. The assembly 32 thus formed serves as a coupling orimpedance matching device to couple a radio device to the transmissionline 3c, and preferably to match the impedance of the radio device tothat of the transmission line. A housing 5E preferably forms a shieldfor the cou pling device 32.

With particular reference to Fig. 2, the wind ings so of the couplingdevice are assembled on the form and the extremities, or leads from thewindings, are connected to solde ing lugs ineluding similar to M andInsulated leads as, 852 and 94 soldered to their respective solderinglugs, as shown by the lead soldered to lug 8d and the lead 94 solderedto lug are adapted for making necessary connections to the couplingdevice. In the preferred form indicated an assembly M73 thus formed ishoused in a cup -shaped member 98 having a false base 96 and an outerbase loll. The coil assembly Hi2 as formed by the form 32, the windings86', and the lugs including 84, which are fastened. to the form 32, issecured to the false base 96 by a bolt liw'l which is anchored to theinner surface of the form 82, and which has a cooperating washer 193 andnut 5%.

A space i ill between the false base Q5 and the outer base lilo, andenclosed within the cupshaped member 538 is preferably filled with aninsulating material such as a heavy wax to weatherproof the unit. Theouter base lei} is fastened to the cup-shaped member 93 by suitable eyebolts i it which have cooperating washers l M and nuts tit. Theconnecting leads are brought out as indicated for the leads and So whichpass through an aperture H23 in the false base and through an aperturelit? in the outer base Hill. To facilitate mounting, a flange Hi2,having a cooperating clamp member is formed on the base mil. Suitablebolts H6 and nuts i28 cooperating with the flange I22 and clamp mernb 1l2, provide means for adjusting the clamp .ltening it on a suitablemountin With particular reference to Fig. 3, he refers to a section of awall of a form E32, upon which a winding may be wound. The sectionalviews of conductor assemblies b4 and S6 show a preferred form ofconstruction for the conductors used in mak ng a winding such as thewinding 38 of l. .=.n the assembly 6 5, which is similar to the assemblyconductors 8 and are surrounded by layers of insulating material it and14 respectively. An outer covering of insulating material 3'53 binds thetwo insulated conductors 68 and "i2 together. By thus forming theconductor assemblies, they may be easily wound adjacent as indicated by6 and Gil on the form 62. After the conduc are wound they may beconnected in series as indicated in and described for 1. In thepreferred construction, layers of in sulating material Si such as paperare wrapped over the winding formed by the conductor assemblies such asie l and 66. Then the shield 63, preferably made of copper or other goodconducting material, is interposed between the insulating material 5iand more insulating material 65. A winding 6. is wrapped over theinsulating material 55. The winding 5'! corresponds to 50 in Fig. 1.

With particular reference to Fig. 4, a form 62 having windingsi3-'tthereon, and soldering lugs lZG, I38 and H56 fastened thereto,forms a coupler sub-assembly The winding connections are made tosoldeing lugs including the lugs M6 i538 and Mt. The sub-assembly I36 ispreferably enclosed within a cup-shaped housing 6 a base Thesub-assembly I30 is i""'ened to the base M4 by a bolt Hi5 which is oredinside the form -52, and which has a cooperating washer M8 and nut ltii.In the preferred form, thus illustrated, the connections to the radiodevice, as explained for the circuit in Fig. 1, are made throughinsulated leads H52 and 554 which are connected to soldering lugsincluding the lug M5), and which pass through an aperture M6 in thecup-shaped member I42. A grommet 58 protects the leads I52 and l5-i fromany sharp edges t at be on the material surrounding the aperture wt, andalso adds additional insulation. Leads I65 and I62 soldered to lugs MSand respectively and also soldered to lugs iiiiwhich are connected toinsulatingly mounted binding posts 565 serve in making connectionsbetween the coupling device and the transmission line as illustrated inand described for Fig. 1. An insulating block Hi8 and a cooperatinginsulating piece I'FB insulate the binding posts 558 from the cup-shapedmember I42. A crew cap ilil having a knurled surface H4 is us d to clampa connecting wire to the binding p t.

With particular reference to Fig. 5, an antenna and a counterpoise aresupported by a mast 2&4. Insulators 286 and 208 insulate the antenna andcounterpoisc respectively, from mast. An insulating terminal block 2H)has mounted thereon conductive terminal strips H2 and 2M, to which theleads 2m and 218 from the antenna 2% and counterpoise respectively, areanchored. The block i ii is supported by the mast and should preferablybe placed about midway between the antenna and counterpoise. A maincoupling device 226 which is similar to that disclosed Fig. 3 is clampedto the mast 255 by a clamp Leads 224 and 226 which preferably insulatedand twisted form a connection between the coupling device 220 and theterminal strips 254 and 252 respectively. Leads .s and form a part ofthe transmission line A cleat 232 supported by the mast 205 by a clampgrips and insulatingly holds the conductors 2228 and 23B, and preventsany strain in the transmission line 234 from being transmitted to thecoupling device 220.

Coupling devices 2 30 are each similar to the device disclosed in Fig.4. The coupling devices are connected to the conductors of thetransmission line 5334 by leads 242 and 244. Leads and 245% on thecoupling devices 24-13 are provided for connections with a radio device.Coupling devices 256 are sim and like reference numerals will refer tosin ar parts. In this form of coupling device, the windings 252 may besimilar to those used on coupling devices 32, 3 and St in Fig. 1, andare wound on a form 254 which is supported by brackets 256 which arefastened to wall mounting plates 258. In this form, the transmissionline 234 may be threaded through conduit pipe 266, and knock-out boxes262 provided at the positions where the coupling devices are to bemounted. By so doing, the wall plate 253 and knockout boxes 2ii2 formthe housing and shield for the coupling device. Leads 255 and Ziit formthe connections between the winding of the coupling device and thetransmission line 23 1. Leads Eiiil and 278 form the connection betweenthe other winding of the con-- pling device and terminals 232 and El iof the binding posts tie and 278 respectively. The binding posts Zl'iiand Z'iii are mounted on an insulating block 28d and thereby insulatedfrom the wall plate 255. The insulating block 286 is fastened to andsupported by the wall plate 2558. Leads 282 and 284 connected to bindingposts 276 and 2'18 respectively form the connections between thecoupling device and a radio device. References 286 and 288 refer to wallstructure of a building.

With particular reference to Fig. 6, a form of insulating material 552has a winding 3B3 corresponding to the winding 38 of Fig, I woundadjacent thereto. Layers of insulating material 6! are interposedbetween the winding SE33 and a shield 63. The shield 63 continues aroundthe unit thus formed, and it should be noted that the ends 3E3 and M5 ofthat shield overlap slightly and are separated by a layer of insulatingmaterial. Hence, the shielding action produced by the shield iselectrostatic rather than electromagnetic. Layers of insulating material65 are then interposed between the shield 63 and a winding El. Thewinding Bl corresponds to of Fig. 1.

In receiving signals a potential diiference is produced between theantenna and counterpoise by the intercepted waves due to the differencein height. That potential difference constitutes the signal voltage, andis transmitted through the coupling devices and transmission line to theradio device. It is apparent to one skilled in the art that if theimpedance of the antenna and counterpoise system is matched to that ofthe line by a suitable coupling device that maximum power transfer willbe obtained between the antenna and counterpoise and the transmissionline. t is also apparent that if the impedance of the transmission lineis matched to that of the radio device by a coupling device that maximumpower transfer will be obtained between the transmission line and theradio device. Hence, it is preferable to have the coupling devices matchthe impedances which they couple. However, an installation such as thatdisclosed in Fig. 5, where several radio devices are coupled to the sametransmission line and an antenna and counterpoise, the impedance of thewindings of the coupling devices 2% which are connected to thetransmission line should preferably be higher than the characteristicimpedance of the line so that the group of couplers together will nottend to short circuit the conductors of the transmission line.

The preferred method of accomplishing the result is to have the sum ofthe impedances of the windings which are connected to the transmissionline equal the characteristic impedance of the line. Another methodmight be to terminate the line in its characteristic impedance and havethe impedances of the windings which are connected to the line so highthat they will not appreciably reduce the effective terminatingimpedance of the line. Another factor in obtaining high energy transferin the coupling devices is that the coefiicient of magnetic couplingbetween the coupled windings of the coupling devices should be kepthigh. Having a high coefficient of coupling prevents losses due toleakage and permits high energy transfer between the windings.

Since the noises and disturbances set up by electrical machinery, streetcars, etc., do not radiate for any great distances, and are picked up toa much greater extent close to the source, it is apparent that thelarger portion of the disturbances picked up by the ordinary antennasystem are picked up by the lead-in and ground wires. In thismodification of the present invention the counterpoise replaces theusual ground connection, and thus permits the pickup of signal energy ata point as far as possible from the source of disturbing energy, andalso permits the close association or twisting of the lead wires of thetransmission line which carry the signal energy from the antenna andcounterpoise. By keeping the conductors of the transmission line closelyassociated, such as by twisting the conductors together, the fieldsintercepted by the conductors are practically equal and thus equalvoltages are produced in the conductors.

The balanced windings such as 29 and 38 01' Fig. 1 which are connectedto the transmission line permit the equal voltages set up in theconductors to buck and neutralize each other without producing a voltagein the associated windings. Having the windings 2i) and 353 formed ofparallel adjacent conductors connected in series as disclosed, helps toelectrostatically balance the winding and reduce the electrostaticcoupling between the windings of the coupling devices, to reduce thetransfer of noise energy between the windings by electrostatic coupling.The shields i2 and interposed between the windings of the couplingdevices also reduce the electrostatic coupling and in that manner ieducenoise.

Inductive coupling in the coupling devices which connect to the radiodevices segregates the radio devices from the transmission line andantenna and counterpoise, so that a number of receivers may be connectedto the same transmission line and antenna and counterpoise withoutinterfering with each other when tuned to the same or diiferentfrequencies. This feature as well as others previously mentioned permitsa single antenna and counterpoise system to supply energy to quite alarge number of radio devices, and thus does away with the necessity ofa maze of wires formerly necessary on large apartments or hotels, aswell as the added feature of noise reduction or elimination.

Two types of coupling devices, 2% and 25!], shown in Fig. 5 are used forthe same purpose, but for different types of installation. Where it ispreferable tomount the coupling devices on the radio set itself orexternal to the building structure, couplers of the type 240 arepreferable. In a new building or in one in which the transmission lineis to be threaded through conduits, couplers of the type 259 arepreferable.

It is preferable for the best operation and proper balancing of thesystem to have the main coupling device 220 mounted near andintermediate the antenna and counterpoise. For that reason, a Weatherproof housing is desirable to keep moisture and corrosive atmosphereaway from the windings of that coupling device when mounted outside.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood. thatother forms might be adopted, all coming within the scope of the claimswhich follow.

What is claimed is as follows:

. In an antenna system, the combination including, a plurality ofimpedance matching de- Vices each having a plurality of windings, onewinding on each composed of a plurality of parallel helically woundconductors insulated from each other and connected in series, another ofsaid windings comprising a helical coil and having a high coefficient ofcoupling with the other winding, a shield interposed between saidwindings and connected to one of said windings and a two wire radiofrequency transmission line con-- necting said parallel woundconductors.

2. In combination in a device of the class described an antenna, atransformer having a pri mary winding connected to said antenna and asecondary winding, a second transformer having primary and secondarywindings, means connecting said last nan secondary winding to a radioreceiver and a transmission line having low attenuation at radiofrequencies connecting the secondary of said first named transformer tothe primary of said second named one, the said con-- nected primary andsecondary each comprising a plurality of helically arranged turns havingthe same winding diameter each turn being formed or two insulatedconductors and an insulating covering surrounding said conductors andsecuring them together as a unitary structure, and lead connecting theconductor of the top end turn with the bottom end turn of the otherconductor.

3. In an antenna system, the combination of an antenna, a radiofrequency transmission line having a characteristic impedance, acoupling device for connecting said transmission line to said antenna, aplurality of similar coupling devices each having two windings, thetotal impedance of all of said windings taken together beingsubstantially equal to the characteristic impedance of said line andleads connecting a plurality of said windings to said transmission line.

4. In a device of the class described, the combination of a long radiofrequency transmission line, means for impressing a broad band of radiofrequency currents across one end of said line, a plurality oftransformers located at spaced apart points on said line and arranged toconnect a plurality of radio receiving devices thereto, each of saidtransformers comprising a coil form, a primary Wound about said form andconsisting of two windings arranged with the turns of one Winding placedbetween the turns of the other, a lead connecting the top turn of onewinding in series with the bottom turn of the other, a layer ofinsulation material surrounding said primary winding and a secondarywinding surrounding said insulation layer and closely coupled to saidprimary winding.

5. In a radio frequency transmission system, the combination of a sourceof modulated signal energy, a long radio frequency transmission linehaving a characteristic impedance, a coupling device for connecting saidenergy source to said transmission line, a plurality of similar couplingdevices spaced apart along said transmission line and each having twowindings and means connecting a plurality of said windings to saidtransmission line, the total impedance of said plurality of connectedwindings being substantially equal to the characteristic impedance ofsaid line.

HOMER J. LOFTIS. MAURICE F. MoCARTI-IY.

